Four-Wavelength Cross-Grating GSE

Figure 10a shows another concept that allows two GSE lasers with different wavelengths to share the same output aperture in a linear, rather than crossed configuration.  In the ideal case, a deep grating on one side of the outcoupler is 100% reflective at the wavelength of the DBR on the opposite side and 0% reflective to the DBR on the same side.  If the gratings are less than ideal, cross talk becomes significant.  Using the concept shown in Fig. 10a in the configuration shown in Fig. 10b provides a GSE laser that can emit four independent wavelengths from a single aperture.  This concept is one of several that can provide 4 wavelengths from a single aperture. Each wavelength can operate at 3.125 Gbps with direct current modulation.  With the addition of the proposed phase-shift modulator, ~160 Gbps over a single fiber from a single aperture is possible.

(a)

(b)

Fig. 10.   a) Concept of a linear two-wavelength GSE laser; b) Concept of a four-wavelength crossed-grating GSE laser.